This invention relates to micro-miniature packaging systems and methods, and more particularly to systems and methods for positioning substrates relative to one another.
Solder bump technology is widely used for electrical and/or mechanical interconnection of substrates. As used herein, substrates can include microelectronic substrates such as integrated circuits and second- or third-level packaging substrates such as printed circuit boards; electro-optical substrates such as substrates including a light emitting diode or laser; optical substrates including a mirror or grating; and sensor substrates that include a sensor. For example, an integrated circuit chip, mirror or laser may be connected to a circuit board or other next level packaging substrate using solder bumps. This connection technology also is referred to as xe2x80x9ccontrolled collapse chip connection-C4xe2x80x9d or xe2x80x9cflip-chipxe2x80x9d technology, and will be referred to herein as solder bumps. Solder bump technology is described, for example, in U.S. Pat. Nos. 6,117,299, 5,892,179 and 5,381,946, the disclosures of which are hereby incorporated herein by reference in their entirety as if set forth fully herein, and need not be described further herein.
It also will be understood that solder bumps are an example of a phase-changeable bump that can be used to position a first substrate relative to a second substrate. Phase-changeable bumps can be controllably changed between liquid and solid phases. Other phase-changeable bump technologies include, for example, waxes, ultraviolet-curable epoxy, thermally-cured epoxy, chemically-cured epoxy, thermoplastics, thermoset plastic, electrorheologic fluids and magnetorheologic fluids. It will be understood that electrorheologic and magnetorheologic fluids are fluids that may contain small polar or ferromagnetic particles that can stick together when exposed to either an electrical or magnetic field, respectively. When the particles stick together, the viscosity of the fluid can increase dramatically. The design and operation of all of these phase-changeable bump technologies are well known to those having skill in the art, and need not be described further herein.
In many applications where a second substrate is positioned relative to a first substrate using phase-changeable bumps therebetween, it may be desirable to precisely control the separation distance, pitch and/or roll of the second substrate relative to the first substrate. For example, when the second substrate comprises an optoelectronic or optical element, such as a laser or mirror, it may be desirable to mount the laser or mirror on a second level package at a precise height, pitch and/or roll, in order to precisely define a desired optical path.
A desired height, pitch and/or roll may be obtained by liquefying the phase-changeable bumps and positioning the second substrate on a first substrate at the desired height, pitch and/or roll using a gripper or manipulator that generally is used to xe2x80x9cpick and placexe2x80x9d integrated circuits on mounting substrates. Unfortunately, however, these grippers or manipulators generally grip, grab or squeeze the second substrate on both faces thereof and/or against the edge wall thereof. Therefore, these grippers or manipulators may have a limited range of height, pitch and/or roll motion, and may also damage the first and/or second substrates during gripping and positioning.
Embodiments of the present invention position a second substrate relative to a first substrate having phase-changeable bumps therebetween, wherein the second substrate has a first face adjacent the first substrate, a second face remote from the first substrate, and at least one edge wall between the first and second faces. The phase-changeable bumps are liquefied to establish an equilibrium position of the first and second substrates relative to one another. At least a portion of the second face is pushed away from the equilibrium position towards the first substrate, to a new position, without applying external force to the first face other than spring forces of the phase-changeable bumps that are liquefied, and without applying external force to any edge wall. Thus, only the spring forces of the phase-changeable bumps that are liquefied oppose the pushing. The phase-changeable bumps that are liquefied then are solidified (i.e., set or hardened), to maintain the new position. In other embodiments, the functionality of the phase change and the spring force may be separated into different sets of bumps.
Embodiments of the invention may arise from recognition that the internal pressure of phase-changeable bumps that are liquefied can be used to create springs. External positioning may be performed by applying forces directed against the spring force, rather than grabbing with manipulators. External setting of height, pitch and/or roll thereby may be provided. After the desired position is achieved, the bumps can be solidified, for example by cooling and/or by chemical means.
In some embodiments of the invention, the second face is pushed away from the equilibrium position towards the first substrate at three spaced-apart points thereon, to define a plane that includes the new position, without applying external force to the first face other than spring forces of the phase-changeable bumps that are liquefied and without applying external force to any edge wall, such that only spring forces of the phase-changeable bumps that are liquefied oppose the pushing. In other embodiments, at least a portion of the second face is pushed away from the equilibrium position towards the first substrate to beyond the new position. Then, at least some of the pushing is released so that the spring forces of the phase-changeable bumps that are liquefied push the second face from beyond the new position to the new position, without applying external force to the first face other than spring forces of the phase-changeable bumps that are liquefied, and without applying external force to any edge wall.
In some embodiments, the equilibrium position places the first and second substrates parallel to one another, and the new position places the first and second substrates oblique to one another. Thus, pitch and/or roll may be adjusted. In other embodiments, the equilibrium position places the first and second substrates parallel to one another, and the new position places the first and second substrates parallel to one another, but closer to one another than the equilibrium position. Thus, height adjustment may be provided. Other combinations of height, pitch and/or roll also may be provided. Accordingly, precise control of height, pitch and/or roll may be obtained without the need to grab the underside or edge of the second substrate with manipulators.